Sustainability in Aquaculture

Sustainability, a concept much discussed in the aquaculture industry, has become associated with the idea that production systems must be designed and sited with consideration of not only their economic viability, but also their long-term environmental and sociological impact. While the concept of sustainable aquaculture has some vocal critics, the industry has been promoting sustainable production as a way of integrating the expertise of producers, researchers, regulators and other interest groups into a process that will advance aquaculture’s technological and economic development. Yet, while the need for sustainability is widely acknowledged, real debate remains over the proper definition and implementation of sustainable aquaculture systems. This continuing debate is largely because sustainability is an interdisciplinary concept that draws on basic and sociological science models, some of which conflict. As a result, the development of sustainable aquaculture is not only a technical challenge, but also a political and perceptional challenge.

Survey approach

A collaborative study between the Aquaculture Research Station and the Department of Agricultural Economics and Agribusiness was initiated to determine whether diverse aquaculture interests groups could collectively develop and agree on economic, environmental and social indicators of aquaculture sustainability. Once identified and weighted, these indicators were to form the basis of a numerical index that could be used to evaluate the relative sustainability of aquaculture production systems in the southeastern United States. The ultimate validity of the index as an evaluation tool hinged on whether a consensus could be developed among a wide variety of participants in the aquaculture industry. A type of panel procedure, known as a Delphi survey process, was used in the study.

Delphi surveys are a way to develop and measure the degree of consensus among experts. A Delphi survey is considered superior to a simple expert survey or focus group because it involves a series of questionnaires (in this case, three rounds) administered to individuals in a manner that protects the anonymity of their responses and thus their ability to freely express opinions. Feedback to the respondents between survey rounds also allows participants to reevaluate their responses based on new information provided by the expert group as a whole without knowing what specific individuals have said. Both the anonymity and feedback features of Delphi surveys have been shown to lead to the unbiased convergence of expert opinion, even among groups that initially hold widely disparate views. For this reason, Delphi surveys, which were originally used in cold-war strategic defense studies, have become widely used in marketing, management and technological evaluation studies.

The experts surveyed in this study came from four different groups that have had direct involvement in the aquaculture sustainability debate: 1) aquaculture producers, 2) aquaculture researchers and extension agents, 3) aquaculture-related regulatory authorities and 4) non-governmental organizations (NGO). The states involved were Texas, Oklahoma, Arkansas, Louisiana, Mississippi, Tennessee, Kentucky, Alabama, Georgia, Florida, South Carolina, North Carolina and Virginia. Of the 163 experts who initially agreed to participate, 121 replied to the first questionnaire for a response rate of 75 percent. By the third round of the survey, the retention rate had increased to 94 percent, with 104 of the original panel participating. These response rates were higher than originally anticipated, making this Delphi survey one of the largest non-defense studies ever done.

Weighting sustainability

As part of each survey round, participants were asked to score the relative importance of the three main facets of sustainability. This information was needed not only to get participants to think about the potential tradeoffs inherent in the sustainability concept, but also for weighting the indicators that would ultimately comprise the sustainability index. Figure 1 shows the revealed weightings across the three survey rounds. In the first round of the survey, participants believed that economic considerations should make up 44 percent of the followed by 36 percent for environmental and 20 percent for social considerations. By the third survey round, participants had increased their weightings for economic considerations 5 percent while decreasing their weightings for environmental and social consideration by 2 percent and 3 percent, respectively.

More important, changing coefficients of variation (CV) across the three survey rounds suggest that the economic and environmental categories developed greater consensus on their relative importance than did the sociological category. These results were consistent with anecdotal evidence, frequently expressed by the survey participants, that aquaculture sustainability should be defined primarily by economic and environmental concerns, with social considerations given subordinate or irrelevant status. However, many NGO participants continued to hold the view that social variables should be an important part of the sustainability criteria even while recognizing the important role of economic and environmental variables.

Specific indicators

Items submitted in round 1 as potential measures of aquaculture sustainability were condensed to avoid duplication into 31 core indicators: 12 environmental, 10 economic and 9 social. The degree of agreement on individual indicators varied considerably, with the highest consensus typically accompanying those indicators with the highest revealed weighting. For example, “water usage” and “profit” had the highest mean weights and lowest CV levels, while indicators like “use of nonnative species” received low mean weightings with the highest CV levels.

The average coefficient of variation fell from 63 percent to 24 percent between rounds 2 and 3, providing an indication that the Delphi survey was successful in creating a significant degree of consensus. This indication was further confirmed by nonparametric statistical analyses of the data using Friedman’s Randomized sustainability index, Block Design, Kendall’s Coefficient of Concordance and a Distance Metric approach. Results of the nonparametric analyses indicated definite rank correlation patterns, rank convergence and rank consensus in the Delphi survey data.

MIDAS model

Having achieved a relatively strong consensus on sustainability categories and indicators, a method of integrating this information into a preliminary index of aquaculture sustainability was needed. A multi-criteria analysis framework provided the basis for this index development. The 31 indicators were combined within three linear sub-indices: environmental, economic and sociological. The contribution (weight) of each indicator was included along with a method for scoring the indicator for a given production system. The scoring system was developed in a way that allowed any indicator to add or subtract from the index the full amount of its revealed weight, depending on its score relative to statute, rule or common practice standards. The final model form was termed Multicriteria Indicators of Delphi-Assessed Sustainability (MIDAS). The MIDAS index used 3- dimensional vector calculations to generate an index score representing the separate environmental, economic and sociological objectives of aquaculture sustainability.

MIDAS has a number of potential applications. If adequate secondary data are available, they can be used to evaluate the production-level sustainability of aquaculture under various input scenarios. In addition, they can be used to analyze the trade-offs that often occur when attempting sustainable aquaculture developments. Such evaluations have been completed and are being refined for warmwater species such as channel catfish and red swamp crawfish. Last, the MIDAS model could be used to clarify the critical economic, environmental or social issues that need further research efforts as the industry continues to move toward sustainable modes of production.